FillQuadLinearColorAntialias paints semitransparent - why ??

[winni]

Hi!

I just did a

Code: Pascal  [Select][+][-]

1. FillQuadLinearColor(Rtop[i],RTop[i+1],RBottom[i+1],RBottom[i],
2.                                           cssGold,cssGold, CSSGoldenrod, CSSGoldenrod);  

Everything is fine. The colors are opaque.
But no AntiAlias. Because of the stairs I changed to

Code: Pascal  [Select][+][-]

1. FillQuadLinearColorAntiAlias(Rtop[i],RTop[i+1],RBottom[i+1],RBottom[i],
2.                                           cssGold,cssGold, CSSGoldenrod, CSSGoldenrod);  

And now the strange thing happens:
The Alpha value seems to be 128.
The colors are semitransparent..

Bug or is there a trick to revert the Alpha values back to 255?

Winni
 

[winni]

Two screenshots about the problem.

Who wants to drink semitransparent beer?

Winni

[circular]

That shouldn't be transparent.

Do you have a simple test program?

[winni]

Hi circular!

Made a little demo of that problem - in the attachment.

Winni

[circular]

Ok I understand.

Well that's normal because when here there are multiple polygons that are adjacent. On the antialias border, pixels are drawn with a certain opacity. When drawing with a certain opacity, the opacities are not added, so in the end you get something transparent.

If you want to draw such adjacent polygons with antialias, you need to use TBGRAMultishapeFiller class of BGRAPolygon unit. There you can give a lot of polygons and draw them in one go.